The present disclosure relates to a semiconductor memory device and a driving method for the same, and more particularly to a MONOS memory and a driving method for the same.
In recent years, with the trend toward higher integration and lower cost in non-volatile semiconductor memory devices, a local trapping MONOS (metal-oxide-nitride-oxide-silicon) memory that has a virtual ground array and traps charge locally has been proposed.
The local trapping MONOS memory however has a problem that the threshold voltage varies when charge is trapped in an ONO (oxide-nitride-oxide) film under in-process charging. It is therefore important to prevent influence of such in-process charging. Also, while emphasis has conventionally been placed on protection against in-process charging for word lines, protection against in-process charging for bit lines has become an indispensable technique as the memory size has become finer.
For example, a technique has been known in which in-process charging to bit lines can be limited to a range of about +7 V to about −1 V and in-process charging to word lines to a range of about ±1 V (see Japanese Laid-Open Patent Publication No. 2001-57389, for example).